[ "O ] 



tion ; but as this operation leaves the powder in grains of various 

 dimenfions, it is forted by being paffed through wire fcreens 

 of progreflive reticulations. Powder is commonly dried in an 

 apartment, three fides of which are furnifted with ledged fhelves 

 containing the compofition, and the fourth is occupied by a large 

 iron ftove, which projeds into the room, but is heated from 

 without. This apparatus is very faulty in many refpeds, but 

 more particularly in not diffufing an equal heat ; an amendment 

 has been attempted, by carrying flues round the drying room, 

 filled with heated fleam ; however the change has been little, if 

 at all, for the better. Perhaps a circular room, with a fpherical 

 ftove in the centre, might communicate a more equal degree of 

 ficcity to the compofition. 



I WILL next fubmit to your lordfliip's examination fome gene- 

 ral obfervations, fele£ted from thofe which occurred during the 

 courfe of my experiments on gun-powder. The powder returned 

 by the navy and garrifons as unferviceable was depofited in the 

 magazine at Purfleet, where that which flill retained its grain 

 was feparated from the duft ; and if two drachms of it, when 

 tried in the vertical eprouvette, had fuflicient ftrength to projed 

 a fuperincumbent weight of twenty-two pounds to the height of 

 three inches and five-tenths, it was again iffued for fervice ; but 

 this happening very rarely, fuggefted a doubt, that by abftrading 

 the duft, our powder was deprived of its principal ingredient i 

 this conjedure I eftabliflied by repeated experiments in the ver- 

 tical and mortar eprouvettes, as the duft (though varying in 

 degree) almoft always exhibited fuperior flrength to the granu- 

 lated 



